Over at Wired, Joe Hanson recounts how researchers Ludovic Orlando and Eske Willerslev used the DNA of modern species to recover the DNA of this long-extinct equine species. He begins:

By piecing together the genetic information locked inside a frozen, fossilized bone, scientists have deciphered the complete genome of an extinct prehistoric horse that roamed the Yukon more than 700,000 years ago. The work rewrites the evolutionary history of the horse and smashes the previous record for the oldest complete genome ever sequenced. In doing so, it redefines how far back in time scientists can travel using DNA sequences as their guide.

Every time a cowboy throws a leg over the saddle and gallops off on his horse, he’s riding on top of 4 million years of evolutionary history. But this history is mostly a mystery. We know surprisingly little about how natural selection and thousands of years of selective breeding by humans have shaped these animals on the genetic scale.

Horses were once considered a textbook example for the smooth transition of one species into another, a perfect illustration of Darwin’s theories. Ancient equine species — dog-sized animals with five toes – gradually evolved into towering, hooved thoroughbreds. Or so the story went. But with every fossil that was unearthed, a more tangled picture emerged.